1. Field of the Invention
The present invention relates to a circuit arrangement for reducing an input voltage, which in particular is pulsed, and to a corresponding method.
2. Description of the Prior Art
It is known to use inductive transducer arrangements for detecting rotary speeds, or rpm. By means of a gear wheel or pulse wheel rotating in front of an induction coil, a voltage proportional to the change in the magnetic field over time and thus to the rpm of the gear wheel is induced in the induction coil. These voltages can be delivered to a threshold stage that furnishes an rpm-dependent signal train.
One such circuit arrangement for generating an rpm-dependent signal train from the periodic voltage of an inductive transducer arrangement is known from German Patent DE 3127220C2for, instance.
For certain applications, it is usual to use gear wheels with a low number of teeth, for instance four teeth, as the pulse wheels. Then, however, the problem arises that during the relatively long intervals between two pulses, interference signals can impair the rpm detection, if their amplitudes exceed a threshold stage of an evaluation circuit. Such interference signals fluctuate to approximately the same extent as the input signal to be evaluated. To circumvent the attendant imprecision in rpm detection, it is known to perform a followup of the threshold value of the threshold value stage as a function of the rpm. The expense for circuitry required to create threshold value followup, however, must be viewed as considerable.